In previous years, a number of risk factors for periodontal disease progression were identified. Project 0005 will determine how therapy alters such risk factors and which risk factors best relate to successful treatment. The Project is divided into 3 phases, pre-therapy, therapy and maintenance. 100 White, 100 Black (non-Hispanic origin) and 100 Type 1 Diabetic subjects > 18 years of age with evidence of prior destructive periodontal disease will be recruited. Subjects will be stratified by age and sex for all groups. At baseline, complete histories including estimates of demographic and environmental variables will be taken. Subjects will be monitored at 3 months pre-therapy, baseline and 3, 6 and 12 months post therapy. clinical parameters taken at 6 sites per tooth at each visit will include: visible supragingival plaque, gingival redness, bleeding on probing, suppuration, subgingival temperature, and duplicate pocket depth and attachment level measurements. Laboratory parameters at each monitoring visit will include: counts of 34 bacterial species in 28 subgingival plaque samples, serum antibody to 12 bacterial species, IL-beta and PGE2 levels in 6 GCF samples and the ability of the "host response" system (PMNs + serum) to kill selected strains of 10 subgingival species. The pre-therapy phase, will compare the subject groups in terms of baseline extent of disease, as well as levels of putative risk factors and rates of disease progression and will explore the relationship between the two. This will provide currently unavailable data describing the subgingival microbiota, host response factors and periodontal disease progression in suspected high risk groups. In the therapy phase all subjects will be treated by scaling and root planing and the effect of this therapy on selected risk indicators and disease progression will be determined. Subjects who show a poor treatment response will be treated further using periodontal surgery and systemic tetracycline and the effects of this therapy on risk factors and disease progression will be re-assessed. The maintenance phase will evaluate subjects post-therapy in order to determine which subjects show disease recurrence during maintenance, which risk factors relate to recurrence and whether such subjects could have been predicted either pre-therapy or at the end of the scaling phase. Some of the Project 0005 subjects will enter studies in Projects 0006 and 0001.